Epidemiological, Serological, and Virological Features of Dengue in Nha Trang City, Vietnam

Abstract

Abstract.Vietnam is endemic for dengue. We conducted a series of retrospective and prospective studies to characterize the epidemiology of dengue and population mobility patterns in Nha Trang city, Vietnam, with a view to rational design of trials of community-level interventions. A 10-year time series of dengue case notifications showed pronounced interannual variability, as well as spatial heterogeneity in ward-level dengue incidence (median annual coefficient of variation k = 0.47). Of 451 children aged 1–10 years enrolled in a cross-sectional serosurvey, almost one-third had evidence of a past dengue virus (DENV) infection, with older children more likely to have a multitypic response indicative of past exposure to ≥ 1 serotype. All four DENV serotypes were detected in hospitalized patients during 8 months of sampling in 2015. Mobility data collected from 1,000 children and young adults via prospective travel diaries showed that, although all ages spent approximately half of their daytime hours (5:00 am–9:00 pm) at home, younger age groups (≤ 14 years) spent a significantly greater proportion of their time within 500 m of home than older respondents. Together these findings inform the rational design of future trials of dengue preventive interventions in this setting by identifying 1) children < 7 years as an optimal target group for a flavivirus-naive serological cohort, 2) children and young adults as the predominant patient population for a study with a clinical end point of symptomatic dengue, and 3) substantial spatial and temporal variations in DENV transmission, with a consequent requirement for a trial to be large enough and of long enough duration to overcome this heterogeneity.

Impact of Climate Variability and Abundance of Mosquitoes on Dengue Transmission in Central Vietnam

“…Human movement, intervention measurements, or vector ecology might explain the difference. A human mobility study in the city of Nha Trang showed that younger individuals spent more time closer to their home than those aged 15-17 years and young adults [40]. That observation suggests that children aged <15 years are at greater risk of bites by the Aedes aegypti mosquito.…”

“…Most dengue studies conducted in Vietnam focused on the northern area (Hanoi) and southern regions [34,[37][38][39]. The central region of Vietnam is also an endemic area for dengue; however, there is little relevant research in this region [40,41]. Therefore, dengue transmission dynamics and relevant environmental risk factors in central Vietnam are not understood.This study aimed to fill the knowledge gap concerning dengue transmission in central Vietnam by investigating the spatiotemporal distributions of dengue outbreaks and evaluating the impact of climate and the vector index on dengue transmission in this region.…”

Chemical Compositions of Crassocephalum crepidioides Essential Oils and Larvicidal Activities Against Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus

“…aegypti are known vectors of yellow fever virus, chikungunya virus, dengue virus, and Zika virus. 21 Dengue fever epidemics are frequent and widespread in Vietnam 22 and chikungunya and Zika infections have been reported. 23 In this work, we have investigated the chemical compositions and mosquito larvicidal activities of essential oils of C. crepidioides collected from wild-growing plants in central Vietnam.…”

Measuring health related quality of life for dengue patients in Iquitos, Peru

“…However, this approach excludes individuals that do not meet the threshold for inclusion (those with the mildest symptoms). To overcome this problem both geographic and contact-cluster strategies screen individuals at higher risk of infection prior to the onset of symptoms, based on their proximity (geographically or socially) to a symptomatic 'index' case [15,16]. This enables the potential recruitment of dengue positive individuals who may ultimately manifest any level of disease severity, including those who would not seek treatment.…”

“…This enables the potential recruitment of dengue positive individuals who may ultimately manifest any level of disease severity, including those who would not seek treatment. A number of cohort studies have successfully used location and contact-based cluster methods to recruit DENV infected individuals in the community who would be unlikely to seek healthcare, yet to our knowledge none have measured HRQoL in enrolled participants [15,16].…”